The present invention relates to a gas jet device for use in respirators, and more particularly to a gas jet device to be connected to a patient circuit for supplying a humidified respiratory gas in a jet state to lungs of a patient through the patient circuit.
FIG. 1 shows a typical example of the conventional repirator, in which a gas source 10 supplies an oscillation ventilator 12 with a respiratory gas at a predetermined pressure level, the gas being oxygen gas or being composed of oxygen gas and air. The oscillation ventilator 12 provides a desired amount of the supplied gas at a predetermined frequency to a patient circuit 16 through a gas jet tube 14. The patient circuit 16 has a gas chamber 18 connected to the gas source 10 through a humidifier 17 for introducing the respiratory gas and an endotracheal tube 20 attached in a communicating relation to the gas chamber 18, the endotracheal tube being inserted from a mouth into a trachea of a patient. The gas chamber 18 is communicated to the atmosphere through a flexible pipe 23. The respiratory gas from the humidifier is passed to his lungs by the respiratory gas jetted from the oscillation ventilator 12. The tube portion 14A of the gas jet tube 14 is a thin tube of about 1 mm diameter, and is inserted into the gas chamber 18 so that the repiratory gas from the oscillation ventilator 12 may be jetted into that chamber. A humidifying tube 22 is inserted into the gas chamber 18 so that the forward end thereof is placed near that of the gas jet tube 14. The humidifying tube 22 is a thin tube of about 1 mm diameter, and is connected to a water source (not shown) for supplying moisture to the respiratory gas from the gas jet tube 14 by dripping water from its forward end.
However, the above-described respirator has a disadvantage in that sufficient moisture is not given to the respiratory gas from the gas jet tube 14 because water drops dripping from the humidifying tube 22 can be blown away or remain in the patient circuit 16, so that they cannot be mixed with the respiratory gas from the gas jet tube 14 in a sprayed state. The prior art respirator has a further disadvantage in that it is difficult to vary the feed of moisture to the respiratory gas supplied from the tube 14 in response to change in flow rate of that respiratory gas.
In order to avoid the above-described disadvantages of the prior art another humidifying structure shown in FIG. 2 has been proposed, in which the gas jet tube 14 is connected at its gas accumulating portion 14B to a water bottle 26 as a water source through a slender tube 28. A check valve 30 and a pump 32 are interposed between the accumulating portion 14B and the water bottle 26.
Although this humidifying structure is capable of spraying water into the respiratory gas, it also has the disadvantage that it is difficult to simultaneously adjust the flow rate of water pumped by the pump 32 in response to change in the feed of the respiratory gas. The above-described humidifying structure has a further disadvantage in that while the respiratory gas is jetted out from the gas jet tube 14, water is not supplied from the tube 28 and thus sufficient moisture is not continuously given to the respiratory gas. This is because when the respiratory gas passes through the tube 14, a high pressure is applied on the open end of the water tube 28 opening to the gas accumulating portion 14B of the gas jet tube 14, so that water in the tube 28 is pushed back toward the pump 32, which necessitates the provision of the check valve 30.